Conventionally, in mobile communication systems, there have been various known techniques to control the handover of a mobile station between different networks (e.g., between a 3GPP standard network and a WLAN, or the like).
Mobile control (handover) in the conventional mobile communication networks is defined in non-patent document 1 and non-patent document 2, for example. Now, a conventional mobile communication system will be described with reference to FIG. 13. A mobile communication system 9 in FIG. 13 is an embodiment of a mobile communication system described in non-patent document 1.
In mobile communication system 9 in FIG. 13, a plurality of access networks (access network A, access network B) are connected to a core network. A UE (User Equipment; mobile station) 910 is also connected to the core network via an access network. UE 910 is connectable to the core network by way of either access network A or access network B.
Here, access network A is a communication path for which QoS can be set, for example a network defined by the 3GPP standard. Provided for access network A is an eNB (base station) 950 to which UE 910 is connected. UE 910 is connected to the core network via eNB 950 and a gateway SGW (Serving GW) 940.
Further, a PGW (Packet Data Gateway: control station) 920 forwarding communication data to UE 910 is installed in the core network. PGW 920 is connected to access network A via SGW 940.
Further, provided for the core network is a MME (Mobility Management Entity: management station) 930 which receives a request for transfer path establishment from UE 910 and takes control of the procedure of establishing an EPS bearer as a transfer path between UE 910 and PGW 920 via eNB 950 and SGW 940. The EPS bearer is a transfer path between UE 910 and PGW 920 by way of access network A.
On the other hand, access network B is provided with an AR (Access Router) 960 to which UE 910 connects, so that UE 910 is connected with PGW 920 in the core network via AR 960 by establishing a transfer path based on DSMIPv6 (Dual-Stack MIPv6) (e.g., see non patent document 3).
UE 910 is connected to PGW 920 by a transfer path, either the DSMIPv6 transfer path or the EPS bearer. A similar transfer path is established at a UE at the other communication end, so that communication between UEs are performed using respective communication paths via PGW 920.
Further, there is a defined handover procedure relating to a case where communication that UE 910 is transmitting/receiving by way of the DSMIPv6 transfer path via access network B is changed over to the bearer transfer path via access network A to continue communication.